MATCHMAKING is a serious--and fast-growing--business, as students learn in a weekend course

Elizabeth Biondi wants to be a matchmaker. After a devastating breakup with a boyfriend last summer, the Detroit social worker decided to channel her romantic energy into something constructive. She had always enjoyed setting friends up on dates--why not strangers? So late last month Biondi, 25, hopped on a plane to New York City and enrolled in matchmaking school.

Biondi is in good company. Dating services have blossomed over the past few years to become a billion-dollar industry. Though the Internet fueled that explosion, real-life matchmakers with names like Great Expectations and It's Just Lunch are popping up around the...